the lower plenum when I pulled the plenum, but now I looked at Nissan's parts fische, and there's supposed to be a "lower insulator" between the rail and lower plenum. I just assumed that the flared hydraulic fitting shaped connection was supposed to provide the seal. Why weren't there any present when I pulled my plenum? I would never have even seen one where it not for the fische. Is this correct that there is an insulator that goes between the fuel rail, at the injector, and the lower manifold. Please advise.